Devices having horizontally-disposed nanofabric articles and methods of making the same

ABSTRACT

New devices having horizontally-disposed nanofabric articles and methods of making same are described. A discrete electromechanical device includes a structure having an electrically-conductive trace. A defined patch of nanotube fabric is disposed in spaced relation to the trace; and the defined patch of nanotube fabric is electromechanically deflectable between a first and second state. In the first state, the nanotube article is in spaced relation relative to the trace, and in the second state the nanotube article is in contact with the trace. A low resistance signal path is in electrical communication with the defined patch of nanofabric. Under certain embodiments, the structure includes a defined gap into which the electrically conductive trace is disposed. The defined gap has a defined width, and the defined patch of nanotube fabric spans the gap and has a longitudinal extent that is slightly longer than the defined width of the gap. Under certain embodiments, a clamp is disposed at each of two ends of the nanotube fabric segment and disposed over at least a portion of the nanotube fabric segment substantially at the edges defining the gap. Under certain embodiments, the clamp is made of electrically-conductive material. Under certain embodiments, the contact between the nanotube patch and the trace is a non-volatile state. Under certain embodiments, the contact between the nanotube patch and the trace is a volatile state. Under certain embodiments, the at least one electrically conductive trace has an interface material to alter the attractive force between the nanotube fabric segment and the electrically conductive trace.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority under 35 U.S.C. § 19(e) to U.S.Provisional Pat. Apl., Ser. No. 60/446,786, filed on Feb. 12, 2003,entitled Electro-Mechanical Switches and Memory Cells UsingVertically-Disposed Nanofabric Articles and Methods of Making the Sameand to U.S. Pat. Apl. No. 60/446,783, filed on Feb. 12, 2003, entitledElectro-Mechanical Switches and Memory Cells Using Horizontally-DisposedNanofabric Articles and Methods of Making the Same, which areincorporated herein by reference in their entirety.

[0002] This application is a continuation-in-part and claims priorityunder 35 U.S.C. § 120 to the following applications which are expresslyincorporated herein by reference in their entirety:

[0003] U.S. patent application Ser. No. 09/915,093, filed on Jul. 25,2001, entitled Electromechanical Memory Array Using Nanotube Ribbons andMethod for Making Same;

[0004] U.S. patent application Ser. No. 10/033,323, filed on Dec. 28,2001, entitled Electromechanical Three-Trace Junction Devices.

[0005] U.S. patent application Ser. No. 10/128,118, filed Apr. 23, 2002,entitled Nanotube Films and Articles; and

[0006] U.S. patent application Ser. No. 10/341,005, filed on Jan. 13,2003, entitled Methods of Making Carbon Nanotube Films, Layers, Fabrics,Ribbons, Elements and Articles.

TECHNICAL FIELD

[0007] The present application relates to devices havinghorizontally-disposed nanofabric articles and to methods of making thesame.

BACKGROUND

[0008] Memory devices have been proposed which use nanoscopic wires,such as single-walled carbon nanotubes, to form crossbar junctions toserve as memory cells. (See WO 01/03208, Nanoscopic Wire-Based Devices,Arrays, and Methods of Their Manufacture; and Thomas Rueckes et al.,“Carbon Nanotube-Based Nonvolatile Random Access Memory for MolecularComputing,” Science, vol. 289, pp. 94-97, 7 July, 2000.) Hereinafterthese devices are called nanotube wire crossbar memories (NTWCMs). Underthese proposals, individual single-walled nanotube wires suspended overother wires define memory cells. Electrical signals are written to oneor both wires to cause them to physically attract or repel relative toone another. Each physical state (i.e., attracted or repelled wires)corresponds to an electrical state. Repelled wires are an open circuitjunction. Attracted wires are a closed state forming a rectifiedjunction. When electrical power is removed from the junction, the wiresretain their physical (and thus electrical) state thereby forming anon-volatile memory cell.

[0009] The NTWCM proposals rely on directed growth or chemicalself-assembly techniques to grow the individual nanotubes needed for thememory cells. These techniques are now believed to be difficult toemploy at commercial scales using modern technology. Moreover, they maycontain inherent limitations such as the length of the nanotubes thatmay be grown reliably using these techniques, and it may difficult tocontrol the statistical variance of geometries of nanotube wires sogrown. Improved memory cell designs are thus desired.

[0010] U.S. Patent Publication No. 2003-0021966 discloses, among otherthings, electromechanical circuits, such as memory cells, in whichcircuits include a structure having electrically conductive traces andsupports extending from a surface of a substrate. Nanotube ribbons aresuspended by the supports that cross the electrically conductive traces.Each ribbon comprises one or more nanotubes. The ribbons are formed fromselectively removing material from a layer or matted fabric ofnanotubes.

[0011] For example, as disclosed in U.S. Patent Application PublicationNo. 2003-0021966, a nanofabric may be patterned into ribbons, and theribbons can be used as a component to create non-volatileelectromechanical memory cells. The ribbon iselectromechanically-deflectable in response to electrical stimulus ofcontrol traces and/or the ribbon. The deflected, physical state of theribbon may be made to represent a corresponding information state. Thedeflected, physical state has non-volatile properties, meaning theribbon retains its physical (and therefore informational) state even ifpower to the memory cell is removed. As explained in U.S. PatentApplication Publication No. 2003-0124325, three-trace architectures maybe used for electromechanical memory cells, in which the two of thetraces are electrodes to control the deflection of the ribbon.

SUMMARY

[0012] The present invention provides new devices havinghorizontally-disposed nanofabric articles and methods of making same.

[0013] Under certain aspects of the invention, a discreteelectromechanical device includes a structure having anelectrically-conductive trace. A defined patch of nanotube fabric isdisposed in spaced relation to the trace; and the defined patch ofnanotube fabric is electromechanically deflectable between a first andsecond state. In the first state, the nanotube article is in spacedrelation relative to the trace, and in the second state the nanotubearticle is in contact with the trace. A low resistance signal path is inelectrical communication with the defined patch of nanofabric.

[0014] Under another aspect of the invention, the structure includes adefined gap into which the electrically conductive trace is disposed.The defined gap has a defined width, and the defined patch of nanotubefabric spans the gap and has a longitudinal extent that is slightlylonger than the defined width of the gap.

[0015] Under another aspect of the invention, the device includesanother electrically conductive trace in spaced relation the patch ofnanotube fabric.

[0016] Under another aspect of the invention, a clamp is disposed ateach of two ends of the nanotube fabric segment and disposed over atleast a portion of the nanotube fabric segment substantially at theedges defining the gap.

[0017] Under another aspect of the invention, the clamp is made ofelectrically-conductive material.

[0018] Under another aspect of the invention, the clamp is made ofelectrically-insulative material having a via therethrough filled withelectrically conductive material to provide an electrical communicationpath with the nanotube fabric segment.

[0019] Under another aspect of the invention, the nanotube fabricsegment is made of a nanofabric having a porosity and wherein theelectrically conductive material filling the via also fills at leastsome of the pores of the of the nanotube fabric segment.

[0020] Under another aspect of the invention, the nanotube fabricsegment has a lithographically-defined shape.

[0021] Under another aspect of the invention, the contact between thenanotube patch and the trace is a non-volatile state.

[0022] Under another aspect of the invention, the contact between thenanotube patch and the trace is a volatile state.

[0023] Under another aspect of the invention, the at least oneelectrically conductive trace has an interface material to alter theattractive force between the nanotube fabric segment and theelectrically conductive trace.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In the Drawing,

[0025] FIGS. 1A-P are cross-sectional diagrams that illustrateintermediate structures created during the process of forming a devicehaving a horizontally disposed nanotube article according to certainembodiments of the invention;

[0026] FIGS. 2A-C are cross-sectional diagrams that illustrate certainembodiments of the invention in which the gap displacement between asuspended nanotube article and an electrode may be controlled duringfabrication and also illustrate a metallization scheme according tocertain embodiments of the invention;

[0027]FIG. 3 illustrates a plan view of an intermediate structureaccording to certain embodiments of the invention;

[0028]FIGS. 4-6 are perspective views of an intermediate structure shownin various cross sectional views according to certain embodiments of theinvention;

[0029]FIG. 7 is a micrograph of an intermediate structure according tocertain embodiments of the invention;

[0030] FIGS. 8A-B and 9 illustrate ways to strap or clamp articles madefrom layers of matted nanotubes with materials, including relatively lowresistance materials, according to certain embodiments of the invention;and

[0031]FIG. 10 is an image of an exemplary nanofabric shown inperspective.

DETAILED DESCRIPTION

[0032] Preferred embodiments of the invention provide new articleshaving horizontally-disposed nanotube articles and provide methods ofmaking same. Some embodiments provide improved ways of clamping orpinching suspended nanotube articles to improve their performance andmanufacturability. Other embodiments provide electromechanical memorycells, which may be discrete or embedded. Under some embodiments, thediscrete memory cells use new approaches to connect to other circuitryor cells, which lowers the resistivity of traces to the memory cells.Still other embodiments provide memory cells that have volatileinformation state (i.e., the information state is lost when power isinterrupted). Some other embodiments use three-trace architecturesanalogous to those of U.S. Patent Application Publication No.2003-0124325. These embodiments however may utilize a combination ofvolatile and non-volatile characteristics; for example, informationstate may be non-volatile, but the device may use a three-tracearchitecture in which the deflection of the nanotube article may becaused by a trace having volatile state characteristics.

[0033] The preferred embodiments are made using nanotube films, layers,or non-woven fabrics so that they form, or may be made to form, varioususeful patterned components, elements or articles. (Hereinafter “films,”“layers,” or “non-woven fabrics” are referred to as “fabrics” or“nanofabrics”.) The components created from the nanofabrics retaindesirable physical properties of the nanotubes and/or the nanofabricsfrom which they are formed. In addition, preferred embodiments allowmodern manufacturing techniques (e.g., those used in semiconductormanufacture) to be employed to utilize the nanofabric articles anddevices.

[0034] Preferred embodiments of the present invention include articlesand methods that increase a strain in the nanofabrics, allowingselectable construction of volatile and non-volatile electromechanicalswitches, including tri-state or tri-trace switches having both volatileand non-volatile states. The nanofabrics in some embodiments alsoprovide for discrete cellular articles, such as memory cells, to bemanufactured.

[0035] Briefly, FIGS. 2A-D illustrate discrete devices that have ananotube article that is suspended relative to two control electrodes.The gap distance between electrode and nanotube article may becontrolled during fabrication to result in different behavior of thedevice. These embodiments, among others, are discussed in more detailbelow.

[0036]FIGS. 3-6 show various plan and cross-section views of a device toillustrate the crossed- and spaced-relationship between the controlelectrodes and the nanotube article for a given cell or device.

[0037] Preferably, the nanotube patch or segment is clamped (above andbelow) up to the portion of the nanofabric article that is so suspended.In addition, preferably, the nanofabric article is connected or joinedto high conductivity signal paths.

[0038] FIGS. 1A-P illustrate how individual, discrete devices or cellshaving nanofabric articles may be made according to preferredembodiments of the invention. (The figures are not to scale.) Theindividual cell includes a patch or segment of the nanofabric suspendedbetween two other traces disposed in crossed-relation to the patch orsegment.

[0039] Referring to FIG. 1A, a silicon wafer substrate 100 with aninsulating or oxide layer 102 is provided. (Alternatively, the substratemay be made from any material suitable for use with lithographic etchingand electronics, and the oxide layer can be any suitable insulator.) Theoxide layer 102 has a top surface 104. The oxide layer 102 is preferablya few nanometers in thickness, but could be as much as 1 μm thick. Theoxide layer 102 is patterned and etched to generate cavities 106 to formsupport structure 108.

[0040] The width W of cavity 106 depends upon the type of lithographicpatterning used. For example, with present photolithography this cavitymay be about 180 nm wide. With other approaches the width may be asnarrow as about 20 nm or smaller. The remaining oxide material definessupports 110 on either side of cavity 106.

[0041] Referring to FIG. 1B, material is deposited in the cavities 106to form a lower electrode 112; the electrode material can be chosen fromany suitable conductor or semiconductor. The lower electrode 112 isplanarized such that its top surface is substantially level with the topsurface 104 of oxide layer 102, forming intermediate structure 114.Lower electrode 112 can be a prefabricated contact plug or a via. Also,lower electrode 112 can be deposited or fabricated in other ways,including by forming on the surface of substrate 102.

[0042] Referring to FIG. 1C, a nitride layer 116 (or any suitableinsulator) is deposited on the surface of structure 114, formingintermediate structure 118. Nitride layer 116 has a top surface 120. Anon-limiting example of nitride thickness is approximately 20 nm for0.18 micron ground rule (GR). The nitride thickness may vary dependingon the ground rule of the desired final product. As explained below,these dimensions can affect certain characteristics of the device; forexample, in the case of a discrete memory cell the parameters maydetermine whether the switch is non-volatile or volatile and may affectthe V_(on) and V_(off) voltages for causing the nanofabric article todeflect.

[0043] Referring to FIG. 1D, nitride layer 116 of structure 118 is thenpatterned and etched to generate cavities 122. The size and shape of thecavity 122 is made to correspond to what will eventually become nanotubeactive regions, i.e., the regions in which nanofabric articles may becaused to deflect. The cavity 122 is formed substantially above lowerelectrode 112, and leaves remaining nitride layer 124 and formsintermediate structure 126.

[0044] Referring to FIG. 1E, a sacrificial layer 128 of polysilicon(having top surface 131) is deposited on the surface of intermediatestructure 126, forming intermediate structure 130. A non-limitingparameter for the thickness T of polysilicon layer 128 is on the orderof 100 to 200 nm.

[0045] Referring to FIG. 1F, the top surface 131 of intermediatestructure 130 is planarized. By doing so the surface 133 of theremaining polysilicon layer 132 is substantially level with the topsurface 120 of remaining nitride layer 124, thus forming intermediatestructure 134.

[0046] Referring to FIG. 1G, a nanotube fabric 136 is applied to, orformed on, the surface of intermediate structure 134, thus formingintermediate structure 138. Non-limiting methods of applying such afabric 136 are by spin coating pre-formed nanotubes, aerosolapplication, dipping or by chemical vapor deposition. Such methods aredescribed in the references listed and incorporated above.

[0047] Referring to FIG. 1H, a resist layer 140 is applied to the topsurface of intermediate structure 138, forming intermediate structure142.

[0048] A region of the resist layer 140 is then patterned. The regionshould be over the area designated for the nanotube active region andshould be larger than such. The resist layer 140 may be patterned byfirst lithographically patterning the resist layer 140 formingintermediate structure 144, as shown in FIG. 11. Structure 144 hasexposed portions 146 of nanofabric on either side of patterned resist148.

[0049] Then, as shown in FIG. 1J, exposed nanotube fabric 146 may beetched away, forming intermediate structure 150. A non-limiting methodof etching the nanotube fabric is by plasma ashing. Structure 150 haspatterned resist 148 with similarly patterned nanofabric portion 141underneath.

[0050] Referring to FIG. 1K, the patterned resist layer 148 is removed,forming intermediate structure 152, having patterned segment or patch154 of nanotube fabric. The patch 154 is over region 132 of sacrificialmaterial which is over electrode material 112. The patch is slightlylonger than the width of the polysilicon region 132.

[0051] Referring to FIG. 1L, a polysilicon layer 156 is deposited overthe top surface of intermediate structure 152 to form intermediatestructure 158. A non-limiting range of polysilicon layer 156 thickness Tis between about 20 to 50 nm.

[0052] Referring to FIG. 1M, the polysilicon layer 156 is patternedforming intermediate structure 162. Structure 162 has a remainingpolysilicon layer portion 160 over the patch of nanotube fabric 154,which as stated above is positioned in what will be a nanotube activeregion. Polysilicon layer portion 160 is larger than what will benanotube active region 122 and is the same size or larger than theunderlying patterned nanotube fabric 154.

[0053] Referring to FIG. 1N, top electrode material 164 is depositedover the top surface of intermediate structure 162, forming intermediatestructure 166. A non-limiting thickness T of electrode material 164 ison the order of about 350 nm. The material for use as top electrode 164can be selected from any metal or conductor suitable for electroniccomponents. Alternatively, depending on the ultimate use of the devicefabricated, this material could be an insulator, e.g., if it were to beused as a nanotube protective layer. The top electrode could also bedefined as a line or a slot landing pad or other structure suitable forinterconnection.

[0054] Referring to FIG. 10, top electrode material 164 is patterned toform upper electrode 168. The top electrode could also be defined as aline or a slot landing pad or other structure suitable forinterconnection. FIG. 10 does not show upper encapsulation material forthe sake of clarity.

[0055] Referring to FIG. 1P, remaining polysilicon layer portion 160 andremaining polysilicon 132 are etched away to create structure 176. Theelectrodes 168 and 112 extend perpendicularly relative to the page andare supported at ends away from the nanotube active area in which thepatch 132 of nanofabric is suspended. The patch 154 is suspended withgaps, e.g., 174, defined by the thicknesses of the sacrificial materialthat was removed, e.g., 160. FIG. 1P does not show upper encapsulationmaterial for the sake of clarity. FIGS. 2A-D, however, illustrate howupper material 178 is used to encapsulate the structure and to assist inclamping the suspended nanotube fabric article.

[0056] The process described above can be modified in many ways. Forexample, the steps corresponding to FIGS. 1I-L may be substituted asfollows. Referring to FIG. 1I′ (which would follow steps correspondingto FIG. 1H), resist layer 140 (see FIG. 1H) is patterned to leavephotoresist 149 and have exposed nanotube portion 147, formingintermediate structure 145.

[0057] Referring to FIG. 1J′, a layer 151 of polysilicon is depositedover what was the exposed nanotube region 147 (see FIG. 1I′) and ontothe remaining photoresist layer 149, forming intermediate structure 153.Polysilicon layer 151 may be any material useful in CMOS processing solong as it is differently etchable over resist layer 140 and the exposednanotubes.

[0058] Then, referring to FIG. 1K′ remaining photoresist layer 149 isremoved in a liftoff process, forming structure 155 with exposednanotube fabric portions 157. The process then continues with thatmentioned above starting with the description of FIG. 1M.

[0059] The exposed nanotube fabric portions 157 may be removed in anashing process, leaving polysilicon layer 151 over nanotube fabricsegment 154, forming structure 162. The remaining polysilicon portion151 is larger than what will be the nanotube active area, similar to thesituation above, and similar subsequent steps may be performed tocomplete the structure.

[0060] FIGS. 2A-C illustrate a metallization and encapsulation schemethat can be used with structure 176 of FIG. 1P. Specifically, thestructure 176 has been encased by insulating material 178. Depending onthe techniques employed the region in which the nanofabric article issuspended may be vacuum.

[0061] The structure so formed is a tri-stable or tri-trace device. Forexample, some of the patent applications identified and incorporatedabove describe various ways in which tri-stable or tri-trace devices maybe used. Among other ways, the tri-trace device may be used as aredundant way in which to activate the suspended nanotube article; maybe used to encode tertiary information; may be used in a push-pullarrangement with the suspended article. In addition, it may be used sothat one trace is used to deflect the nanotube article into contact withan electrode, and the other trace may be used to release the nanotubearticle from contact.

[0062] The nanoswitch in structure 182 has been encased by insulatingmaterial 178, and has a gap height 180. In some embodiments, the gapheight 180 is a function of the thickness of sacrificial polysiliconlayers 132, 160 (see FIG. 1(O) above). Upon deflection, the nanofabriccontacts the lower electrode 112 forming a stable van der Waalsinteraction yielding a non-volatile switch.

[0063] Structure 183 illustrates a nanofabric based switch having aninsulation layer 185 over one electrode. (Fabrication of such anoxidized electrode is explained below in Example 3.) The insulationlayer 185 may be used to change the characteristics of the switch to bevolatile or to provide further assurance of desired behavior. Theinsulating layer (which alternatively may have been placed on the facingsurface of electrode 168) may be used to prevent different fibers fromthe nanofabric element from simultaneously electrically contacting bothelectrodes (112, 168) during a state transition. Such contact mayprevent or hinder switching of the fabric between states.

[0064] Compare structures 182 and 183, which may be used as non-volatileswitches, to structure 188 which illustrates a volatile switch. Instructure 188 the gap height 186 between the nanofabric 172 and theunderlying electrode 112 has been increased such that the strain energyof the stretched nanofabric overcomes the van der Waals attractionbetween the fabric and the electrode. The nanofabric forms part of aclosed circuit and returns to its non-deflected, open circuit state. Itshould be noted that the effect of the van der Waals interaction betweennanofabrics and other elements can be affected at their interface(s).The effect may be enhanced or diminished; e.g., the attractive force canbe diminished by coating the surface of the electrode with a thin layerof oxide or other suitable materials. A purpose of this diminishing ofattractive forces may be to create volatile nanoswitches; such volatileswitches may be especially useful in applications such as relays,sensors, transistors, etc.

[0065] In the embodiment of FIG. 2A, the electrode or electrodes may beactivated relative to the patch 154 to cause the patch 154 to deflectand contact the lower electrode 112. In this case, this forms a stablevan der Waals interaction. The deflection of the patch also creates arestoring force to restore the patch to horizontal (non-deflected) stateshown in FIG. 2A. This restoring force is a function of, among otherthings, the geometry of the device, e.g., the distance (180) which thepatch 154 is deflected. In this embodiment, the van der Waals forcewhich keeps the patch 154 in contact with the electrode 112 is largerthan the restoring force resulting from the geometry of FIG. 21,yielding a non-volatile switch. That is, when power is removed, the vander Waals force that holds the patch 154 in contact with electrode 112is greater than the restoring force on the patch 112, and thus the patchwould remain in a deflected state.

[0066] Compare this situation to the structure 188 of FIG. 2C. In FIG.2C, the gap distance 186 is larger creating a larger restoring force. Byappropriate control of the gap distances (via creation of thesacrificial material) this gap may be made large enough to create arestoring force that is greater than the van der Waals force.Consequently, the device of FIG. 2C would be volatile. The patch 154could be deflected similarly to that described above, but the restoringforce would be large enough to cause the patch 154 to return to thehorizontal state if power were interrupted. The nanoribbon can deflectvia electrostatic attraction but the van der waals force by itself isnot sufficient to hold it there. In structure 188 the gap height 186between the patch 154 and the underlying electrode 112 has beenincreased such that the strain energy of the stretched nanofabricovercomes the van der Waals attraction between the fabric and theelectrode. The nanofabric forms part of a closed circuit and returns toits non-deflected, open circuit state.

[0067]FIG. 2D illustrates structure 192. Structure 192 illustrates anon-volatile switch where deflected nanofabric 154 contacts lowerelectrode 112 closing a circuit and remains in contact keeping thecircuit closed indefinitely. If the gap height 180 of structure 192 weresufficiently large as in structure 188 then the deflected state of thenanofabric 172 would not remain indefinitely.

[0068] By properly supporting nanofabric 154, the amount of deformationof the nanofabric 154 can be affected. For example, as shown in FIG.2(A), the nanofabric 154 may be “pinched” at the edges of the openregion 194 left after removal of sacrificial polysilicon layer 132,previously shown in FIG. 1(O). Having upper and lower pinching supportaround nanofabric 154 can increase the strain on the nanofabric 154. Insome embodiments, this type of pinching support at the edges of the openregion 194 creates volatile switches which would otherwise benon-volatile. By controlling the design and manufacture of thenano-switch assembly as described here, it is possible to selectablyprovide tri-state non-volatile structures and/or volatile structures.

[0069] Using discrete nanofabrics articles and electrodes in thisfashion permits formation of discrete devices and cells. For example,these cells may be used in digital memory devices. The nanofabrics, e.g.154, and electrodes, e.g. 168, may extend above the substrate and/orsupports 102 sufficiently to allow an electrical connection to be madeto the nanofabrics 154 and electrodes 168. Such connections may be madeby any suitable method, such as by etching or exposure to form a channel196 (not to scale) or via connecting the nanofabrics 154 with anactivation electrical signal.

[0070] Channel 196 is used for electrically connecting an element of theswitch, e.g. nanofabric 154, to an activation (read/write) line. Thechannel 196 may subsequently be filled with a conductor to achieve theactivation connection, or may be formed by some other technique.

[0071] One aspect of the present invention is directed to formation ofconductive composite junctions whereby a suitable matrix material isdisposed within and around the nanotubes or fibers of a nanofabric orother porous nano material. Such junctions can provide desirablemechanical and/or electrical properties. For example, electrical contactbetween a nanofabric and a metal connection or activation point may beenhanced, or the contact resistance may be decreased by applying themetal contact as a matrix material impregnating the nanofabric tubes.Also, mechanical contact and strain may be increased as a result of theincreased contact between the nanotubes and the matrix material.

[0072] For example, with reference to FIG. 2D, activation connectionchannel 196 extends down to the nanofabric 154. Then a metal filling thechannel 196 may further be introduced into the pores of nanofabric 154,in region 194. The matrix material extends down to the underlyingnitride layer (or any other layer) below the nanofabric 154. The effectof such a connection can be to secure the nanofabric 154 and increasethe strain on the nanofabric 154. Also, the electrical connectionbetween nanofabric 154 and the activation connection is increased. Othermethods of securing the nanofabric to the supports are envisioned andone is explained in Example 2, below.

[0073] Almost any material (insulating or conducting) can be made topenetrate into or through a porous thin article such as a nanofabric.This may be done to improve the mechanical pinning contact and increasereliability and manufacturability, or to improve electrical connectionwith the nanofabric and reduce contact resistance to the nanoarticle.Depending on the materials used, a bond may form between the penetratingmatrix material and the material below the nanofabric. Examples ofmaterials which can be used to secure a nanofabric in this way includemetals and epitaxial silicon crystal materials. Other uses for suchjunctions are possible, for example in the manufacture of permeable basetransistors. It is worth noting that the composite junctions andconnections described above do not cause a disruption in the fabric ofthe nanofabric materials into which the impregnating matrix material isintroduced. That is, connection channel 196 does not itself cut throughthe nanofabric 154, but rather just allows a filler matrix material toflow into and through the nanofabric 154 and connect it to othercomponents of the device. In some cases it may be desirable to use aconductive filler to reduce resistance of the nanofabric or contacts tothe nanofabric.

[0074]FIG. 3 illustrates a view of intermediate structure 176 (see FIG.1P) directly from above. An oxide layer 102 supports a nanofabric 154and nitride layers 116 support electrode 168. Cross sections A-A′, B-B′and C-C′ are shown for reference. Upper encapsulation material 178 (seeFIG. 2A) is omitted for clarity.

[0075]FIG. 4 is a perspective view of intermediate structure 176 takenat cross section A-A′ shown in FIG. 3. FIGS. 5 and 6 perspective viewsof intermediate structure 182 taken at cross sections B-B′ and C-C′(structure 176 is structure 182 with the top insulating layers removedfor clarity). (In FIGS. 4-6 upper material 178 is shown.)

[0076]FIG. 4 is an illustration of the elements of the device of FIG. 3,as viewed along cross section at A-A′. (Again encapsulating material 178is removed from the figure for clarity.) At this portion of thestructure, which is away from the nanotube active region, the upperelectrode 168 is disposed on top of nitride layer 116.

[0077] FIGS. 5(A)-(B) illustrate two views of the structure as viewedalong cross-section B-B′. In these instances the structure 182 includesthe encapsulating material 178 and corresponds to the view of FIGS.2A-B. FIG. 5A shows the view along cross section B-B′, and FIG. 5B showsthe view along cross-section B-B′ and again in cross section along C-C′.

[0078] These views show the patch 154 suspended in an active regionbetween an upper electrode 168 and lower electrode 112. As stated above,and explained in the identified and incorporated patent applications,the electrodes may be used to cause the patch 154 to deflect up or down.The patch 154 is clamped by material from above and below to the edge ofthe nanotube active region, where the patch is suspended 154 and may becaused to deflect as shown in FIG. 2C. In this embodiment, thedisplacement D of FIG. 2C has been substantially removed. A substratelayer 100 supports an oxide layer 102. A lower electrode 112 is disposedbelow and not in contact with nanofabric 154 which is fixed toinsulating layer 178 and insulating layer 116 supports electrodematerial 168. For the sake of clarity, the patch 154 is not illustratedwith an electrical contact, but metalization techniques such as thosedescribed in connection with FIG. 2C may be employed. As stated above,the gaps between the patch 154 and corresponding electrode may becontrolled to create either volatile or non-volatile states.

[0079]FIG. 6 illustrates the elements of structure 182 as viewed alongcross section C-C′. The patch 154 in this cross section does not appearto be contacting any other element, but as can be seen in FIGS. 5A-B,the patch is contacting and clamped by other elements, e.g. insulatinglayer 178 (not shown in FIG. 6). The exploded view (shown within thedotted lines) illustrates the interrelations of substrate 100,insulating layer 102, nitride layer 116 and electrodes 112 and 168, aswell as the location of patch 158 in reference to the aforementionedelements.

[0080] The structures depicted above may be used asnano-electromechanical switches and can be created to have a volatile ornonvolatile state (as manifested by the deflected state of patch 154)depending on the aspect ratio of the lengths a and b, were a is thedistance between the undeflected nanofabric and the electrode (i.e., thegaps 180 or 186 of FIGS. 2A-B), and b is the length of the nanofabricwhich deflects. If the strain energy of the deflected nanofabric is lessthan the van der Waals force holding the nanofabric in contact with thelower electrode, then the switch will be non-volatile. If however thestrain energy can overcome the van der Waals attraction, then the switchwill behave in a volatile manner and a circuit will be closed onlyfleetingly.

[0081] Furthermore, the switch may be volatile with regard to topelectrode 168 and non-volatile with regard to lower electrode 112, orboth volatile or both non-volatile.

[0082]FIG. 7 is an actual micrograph of a working nano-fabric-basedswitch. The fabrication of the switch is described in Example 2, below.In this micrograph, only a few nanotubes of a given patch appear infocus but can be seen spanning the channel formed. (The device omits anupper encapsulating material 178, as shown in FIG. 2A.)

EXAMPLE 1

[0083] To fabricate the nonvolatile nanotube switch a silicon wafer witha thermally grown oxide (0.5 μm) is employed.

[0084] Embedded electrodes are constructed by electron beam lithography(EBL) with polymethylmethacrylate (PMMA) as resist. After the electrodepattern is defined in the resist, Reactive Ion Etching (RIE) is employedwith CHF₃ gas to construct a trench in the oxide. The embeddedelectrodes are constructed by a lift-off process by depositing theelectrode in an electron beam evaporator to fill the trench and thenstripping of the resist in N-methyl pyrolidone at 70° C. (Shipley 1165).The electrodes are 0.18±0.02 μm wide and consist of 850 Å of metal(Titanium, Ti) and 200 Å of a sacrificial material (Aluminum oxide,Al₂O₃). The vertical gap between electrodes and the as yet depositedSWNTs was adjusted at 200±50 Å to yield electromechanically switchablebits as predicted theoretically. This gap of 200±50 Å corresponds to atensile strain of ε_(tensile)=0.9±0.5% of the nanotubes in the ON state,which lies well within the elastic limit of SWNTs. A silicon or metalbeam, however, could not withstand this tensile strain withoutpermanent, plastic deformation.

[0085] After the creation of the embedded electrodes, the carbonnanotube fabric is constructed. The nanotube fabric is produced byspin-coating a solution of SWNTs in 1,2 dichlorobenze(ortho-dichlorobenzene, ODCB) on the device wafer. The concentration ofthe nanotube solution is 30±3 mg/L. The solution is sonicated in anultra-sonic bath (70 W sonication power) for 90 minutes to fullydisperse the nanotubes. After sonication, the nanotube solution is spunonto the wafer utilizing typical photoresist spinning techniques.Multiple spins were required to produce the desired sheet resistance ofthe SWNT fabric of <100 kΩ/square. The sheet resistance of the nanotubemonolayer can be reliably varied between 10 kΩ/square and severalMΩ/square by adjusting the concentration of the nanotube solution andthe number of spin-coating steps. For the devices discussed here, a SWNTsheet resistance of 75 kΩ/square was chosen.

[0086] Once the desired nanotube fabric sheet resistance and density isobtained, positive i-line photoresist is spin-coated on the SWNTs (e.g.Shipley 1805 resist). The patterning of the nanotubes, however, is notlimited by the type of photoresist employed, since various types ofresist have been used. The photoresist-coated wafer is then exposed anddeveloped to form the desired pattern. After development of the pattern,the exposed carbon nanotubes can be removed cleanly by isotropic ashingin oxygen plasma while the nanotubes underneath the photoresist areprotected from oxidation. Typically an isotropic oxygen plasma of 300 Wpower was used for removing the exposed SWNTs at a pressure of 270 mtorrand an ashing time of 9 minutes. The photoresist is then subsequentlystripped in N-methylpyrollidinone (NMP) and a SWNT film pattern isexposed. Patterned SWNT stripes were typically 100 μm long and 3 μmwide, although stripes with widths as small 0.25 μm have also beenfabricated.

[0087] In a subsequent, aligned EBL step, clamp lines (Ti, 1000 Å thick,0.18±0.02 μm wide) are defined by liftoff in PMMA resist on top of theSWNT stripes, parallel to the embedded electrodes (distance of 1000 Å toelectrode). These clamps are necessary to prevent uncontrolled adhesionof the SWNTs to the lower electrode upon removal of the sacrificiallayer in the next step. Subsequently, the device electrodes and SWNTstripes were interconnected to bond pads so that individual junctions ona die could be electrically tested. The distance between SWNT stripemetallization and switching junction is 3 μm. Finally, the patternedSWNTs were suspended by wet chemical removal of the Al₂O₃ sacrificiallayer in an aqueous base (ammonium hydroxide, NH₄OH), followed by rinsein deionized water (DI) and isopropanol (IPA). Subsequently, the devicedie were hermetically packaged.

[0088] Programmable nanotube memory devices fabricated according to thisprocedure were programmed by sweeping the voltage over the junctionusing the programmable voltage source of a Keithley Electrometer.Simultaneously, the current that flew over the junction was measuredusing the integrated current preamplifier (10 fA sensitivity) of theelectrometer to generate current vs. voltage curves (I-V curves). Forall measurements the SWNTs were biased high, while the underlyingelectrode was held at ground. Current vs. voltage (I-V) measurementsshowed an abrupt increase in current over the nanotube-electrodejunctions at a threshold voltage of 2.5±0.5 V as the SWNTs switched froma suspended, high resistance (>MΩ) OFF state into contact with theunderlying electrodes to form an ohmic (˜kΩ) ON state. The nanotube bitstate was retained even when power was disconnected for several days(i.e., the switched bits are nonvolatile).

EXAMPLE 2

[0089] A wafer (32-04, Die E4, Device 9x26/4x17) is coated in resist andpatterned with standard optical lithographic technique, the pattern wastransferred to the SiO₂ by reactive ion etch (RIE) in CHF₃ for 4minutes.

[0090] A Cr/Au 5/50 nm marker was used for EBL alignment (via thermalevaporation). The resist and the metal above the resist were removed bya standard liftoff in N—N Dimthyl pyrolidone (1165). The wafer was ashedin O₂ plasma for 5 min PMMA. (Microchem), was applied by spin coating 60seconds at 4000 rpm.

[0091] Electron bean lithography (EBL) was performed to make EBLmarkers, PMMA was developed and the pattern was etched into the SiO2 inCHF₃ for 4 min. 5/50 nm Cr/Au was deposited, and a liftoff was performedas above to leave the EBL markers. PMMA was applied, and EBL wasperformed to create the lower electrode pattern. The PMMA was developedwith MIBK. RIE was performed in CHF3 for 4:30 minutes to transfer thepattern to the SiO₂.

[0092] 85/20 nm Ti (conductor)/Al₂O₃ (sacrificial layer) was ElectronBeam deposited, and lifted off as described above to create the lowerelectrodes.

[0093] Atomic Force Microscopy (AFM) was performed to determine theunder/overfill of the lower electrode, the electrodes were underfilledby −2 nm).

[0094] Laser ablation-grown nanotubes in solution were spun on to thewafer, 8 times to produce a film with a 50 KiloOhm resistance (500 rpmfor 30 sec. and 2000 rpm for 20 seconds, 8 times).

[0095] Photoresist was spun onto the nanotube fabric (1 Min 400 rpm).The resist was patterned and developed and the wafer was ashed in an O₂plasma for 3 min at 300 W three times, with 5 minute intervals to removethe exposed nanotubes. The remaining resist was removed in 1165(Shipley). PMMA was applied as above, and EB lithography was performedto create a pattern of clamps which attach the nanotube fabric moresecurely to the underlying supports, (100 nm Ti). Interconnects (notshown in the micrograph) are created by first applying and developingresist as above, and upper interconnect metal material (10/10/250/10Cr/Au/Cu/Au) was deposited and a lift off procedure was performed. Thesacrificial Al₂O₃ layer was removed by wet etch in 4:1 Deionizedwater:351 (Shipley) (an NaOH based developer). The junction shown inFIG. 7 was created by the method outlined in Example 2. The lightvertical stripes are raised supports; the single dark stripe is a lowerelectrode below suspended nanotubes. Because of the resolution of theelectron microscope, the image does not clearly show the nanotubes, itdoes, however show the geometry of the switch.

EXAMPLE 3

[0096] A junction created as described in Example 2 was oxidized inorder to increase the reliably volatile aspect of switches as follows:

[0097] Five standard cubic centimeters per minute (sccm) of O₂ wasflowed over an NRAM switch, ac voltage (triangle wave) was applied tothe NRAM junction (5 V amplitude, 10 kHz frequency).

[0098] Amplitudes lower than 2 V are not high enough to make the switchvolatile. Amplitudes higher than 7 V frequently destroy the device (veryhigh to infinite resistance afterwards). It was found that the switchturns volatile within a few seconds of application of voltage in thepresence of the O₂, after which, the switch remained volatile. 5Vamplitude of ac wave adequately oxidizes the electrode; however voltageamplitudes of 2 V-7 V have been successfully used for fabricatingvolatile devices.

[0099]FIGS. 8A-9 illustrate various ways in which a nanotube fabric maybe clamped or pinched or strapped by various materials including metalcoverings. This may be done to better hold the nanotube patch and toprovide low resistance interconnect to the patch.

[0100]FIG. 8(A) illustrates a framed portion of nanofabric and a methodof its creation. Such a framed nanofabric may be created by firstcreating a fabric 802 on a substrate, as illustrated by intermediatestructure 800, covering the fabric 802 with an appropriate coveringmaterial 812, as shown illustrated by intermediate structure 810, andpatterning and removing a section of the covering material 812, e.g. bylithography leaving a “frame” of material around exposed fabric, asshown in intermediate structure 814. Such a strapping method is morefully described in “Non-volatile Electromechanical Field EffectTransistors and Methods of Forming Same” US Provisional PatentApplication, filed Jun. 9, 2003, serial No. 60/476,976. The coveringmaterial may be conductive, and may act to alter the electricalproperties of the entire patterned fabric, or it may be semiconductingor insulating. The material of the strapping layer should be selectivelyetchable over nanofabric when used alone to open up a window of exposedfabric. The material of the covering layer may be selectively etchableover an intermediate layer disposed between the nanofabric and coveringlayer. The intermediate layer in this case may act as an etch stop whenetching and patterning the covering layer.

[0101]FIG. 8(B) illustrates a patterned fabric where no frame is formed,rather a set of disconnected sections of covering layer are formed,disconnected sections may be electrodes and have particularly usefulapplication for resistance modulation detection structures. Intermediatestructure 810 is patterned to form electrodes 818, as illustrated inintermediate structure 816.

[0102]FIG. 9, intermediate structure 900, illustrates yet another methodof forming nanofabric-based devices. Such a method involves a coveringmaterial 902 that is selectively etchable over an intermediate layer904. Covering material 902 is preferably metal, and intermediate layeris preferably a semiconductor, e.g. silicon, however any suitablematerial for the application will work. The intermediate layer 904 isdisposed between the nanofabric 906 and covering layer 902. Theintermediate layer 904 in this case may act as an etch stop when dryetching and patterning the covering layer 902. Intermediate structure910 illustrates patterned covering layer 912 in the shape of a frame,however any pattern will work depending on the requirements of the finalproduct. Intermediate structure 910 is subjected to an annealing step(forming structure 916) whereby covering layer 902 and intermediatelayer form a conducting composite layer 914, e.g. a metal silicide. Sucha composite layer can act as stitching electrode or other contact oraddressing element, depending on the use of the final product.

[0103]FIG. 10 is an image of an exemplary fabric of nanotubes shown inperspective. As can be seen, the fabric may be highly porous and appearas several threads with gaps in between. In this figure there areactually several ribbons of nanofabric extending from left to rightseparated from one another by areas with no nanotubes. One may noticethat the fabric of FIG. 7 is likewise very porous with a few nanotubesspanning the channel and contacting electrodes. In both figures, theresolution of the figure is affected by the imaging technology so somenanotubes may not appear in focus or be noticeable.

[0104] Other Variations

[0105] Note that the electrodes, e.g. the top electrode 168, maythemselves be formed of nanofabric materials. In some embodiments,having a nanofabric ribbon or other nanofabric article disposed abovethe movable nanofabric element 172 instead of a metallic electrodepermits removal of sacrificial materials from below the top electrode.Fluid may flow through a nanofabric material disposed above asacrificial layer to remove the sacrificial material. Likewise, thelower electrode may be formed of a nanofabric material if desired.

[0106] Under certain preferred embodiments as shown in FIGS. 2(A)-(B), ananotube patch 154 has a width of about 180 nm and is strapped, clamped,or pinned to a support 102 preferably fabricated of silicon nitride. Thelocal area of lower electrode 112 under patch 154 forms an n-dopedsilicon electrode and is positioned close to the supports 110 andpreferably is no wider than the patch, e.g., 180 nm. The relativeseparation from the top of the support 102 to the deflected positionwhere the patch 154 attaches to electrode 112 (FIG. 2(B)) should beapproximately 5-50 nm. The magnitude of the separation (180 or 186) isdesigned to be compatible with electromechanical switching capabilitiesof the memory device. For this embodiment, the 5-50 nm separation ispreferred for certain embodiments utilizing patch 154 made from carbonnanotubes, but other separations may be preferable for other materials.This magnitude arises from the interplay between strain energy andadhesion energy of the deflected nanotubes. These feature sizes aresuggested in view of modern manufacturing techniques. Other embodimentsmay be made with much smaller (or larger) sizes to reflect themanufacturing equipment's capabilities.

[0107] The nanotube patch 154 of certain embodiments is formed from anon-woven fabric of entangled or matted nanotubes (more below). Theswitching parameters of the ribbon resemble those of individualnanotubes. Thus, the predicted switching times and voltages of theribbon should approximate the same times and voltages of nanotubes.Unlike the prior art which relies on directed growth or chemicalself-assembly of individual nanotubes, preferred embodiments of thepresent invention utilize fabrication techniques involving thin filmsand lithography. This method of fabrication lends itself to generationover large surfaces especially wafers of at least six inches. Theribbons should exhibit improved fault tolerances over individualnanotubes, by providing redundancy of conduction pathways contained withthe ribbons. (If an individual nanotube breaks other tubes within therib provide conductive paths, whereas if a sole nanotube were used thecell would be faulty.)

[0108] While the inventors typically desire a monolayer fabric ofsingle-walled nanotubes, for certain applications it may be desirable tohave multilayer fabrics to increase current density, redundancy or othermechanical or electrical characteristics. Additionally it may bedesirable to use either a monolayer fabric or a multilayer fabriccomprising MWNTs for certain applications or a mixture of single-walledand multi-walled nanotubes. The previous methods illustrate that controlover catalyst type, catalyst distribution, surface derivitization,temperature, feedstock gas types, feedstock gas pressures and volumes,reaction time and other conditions allow growth of fabrics ofsingle-walled, multi-walled or mixed single- and multi-walled nanotubefabrics that are at the least monolayers in nature but could be thickeras desired with measurable electrical characteristics.

[0109] The effect of the van der Waals interaction between nanofabricsand other elements can be affected at their interface(s). The effect maybe enhanced or diminished; for example, the attractive force can bediminished by coating the surface of the electrode with a thin layer ofoxide or other suitable chemicals. Volatile nanoswitches may also bemade by employing such techniques instead of or in addition tocontrolling the gap dimension between a patch and electrode. Suchvolatile switches may be especially useful in applications such asrelays, sensors, transistors, etc.

[0110] As the vertical separation between the patch and the underlyingelectrode increases, the switch becomes volatile when the deflectednanofabric has a strain energy greater than that of the van der Waalsforce keeping the fabric in contact with the underlying electrode. Thethicknesses of insulating layers which control this separation can beadjusted to generate either a non-volatile or volatile condition for agiven vertical gap as called for by particular applications with desiredelectrical characteristics.

[0111] Other embodiments involve controlled composition of carbonnanotube fabrics. Specifically, methods may be employed to control therelative amount of metallic and semiconducting nanotubes in thenanofabric. In this fashion, the nanofabric may be made to have a higheror lower percentage of metallic nanotubes relative to semiconductingnanotubes. Correspondingly, other properties of the nanofabric (e.g.,resistance) will change. The control may be accomplished by directgrowth, removal of undesired species, or application of purifiednanotubes. Numerous ways have been described, e.g. in the incorporatedreferences, supra, for growing and manufacturing nanofabric articles andmaterials.

[0112] The U.S. patent applications, identified and incorporated above,describe several (but not limiting) uses of nanofabrics and articlesmade therefrom. They also describe various ways of making suchnanofabrics and devices. For the sake of brevity, various aspectsdisclosed in these incorporated references are not repeated here. Forexample, the various masking and patterning techniques for selectivelyremoving portions of the fabric are described in these applications; inaddition, various ways of growing nanofabrics or of forming nanofabricswith preformed nanotubes are described in these applications.

[0113] As explained in the incorporated references, a nanofabric may beformed or grown over defined regions of sacrificial material and overdefined support regions. The sacrificial material may be subsequentlyremoved, yielding suspended articles of nanofabric. See, for example,Electromechanical Memory Array Using Nanotube Ribbons and Method forMaking Same (U.S. patent application Ser. No. 09/915,093) filed Jul. 25,2001, for an architecture which suspends ribbons of nanofabric.

[0114] The articles formed by preferred embodiments help enable thegeneration of nanoelectronic devices and may also be used to assist inincreasing the efficiency and performance of current electronic devicesusing a hybrid approach (e.g., using nanoribbon memory cells inconjunction with semiconductor addressing and processing circuitry).

[0115] It will be further appreciated that the scope of the presentinvention is not limited to the above-described embodiments but ratheris defined by the appended claims, and that these claims will encompassmodifications and improvements to what has been described.

What is claimed is:
 1. A discrete electromechanical device, comprising:a structure including an electrically-conductive trace; a defined patchof nanotube fabric disposed in spaced relation to the trace; and whereinthe defined patch of nanotube fabric is electromechanically deflectablebetween a first and second state, wherein in the first state thenanotube article is in spaced relation relative to the trace, andwherein in the second state the nanotube article is in contact with thetrace; and a low resistance signal path in electrical communication withthe defined patch of nanofabric.
 2. The discrete electromechanicaldevice of claim 1 wherein the low resistance signal path is a metalsignal path in contact with the defined patch of nanotube fabric.
 3. Thediscrete electromechanical device of claim 1 wherein the structureincludes a defined gap into which the electrically conductive trace isdisposed, wherein the defined gap has a defined width, and wherein thedefined patch of nanotube fabric spans the gap and has a longitudinalextent that is slightly longer than the defined width of the gap.
 4. Adiscrete electromechanical device, comprising: a structure including afirst and second electrically-conductive trace disposed substantiallyparallel to one another and in a spaced relation relative to oneanother; a defined patch of nanotube fabric disposed between the firstand second trace and extending substantially perpendicular to the firstand second traces, wherein the defined patch of nanotube fabric iselectromechanically deflectable into contact with at least one of thefirst and second traces in response to electrical stimulation of atleast one of the first and second traces relative to the defined patchof nanotube fabric; and a low resistance signal path in electricalcommunication with the defined patch of nanofabric.
 5. The discreteelectromechanical device of claim 4 wherein the low resistance signalpath is a metal signal path in contact with the defined patch ofnanotube fabric.
 6. The discrete electromechanical device of claim 4wherein the structure includes a defined gap into which one of theelectrically conductive trace is disposed, wherein the defined gap has adefined width, and wherein the defined patch of nanotube fabric spansthe gap and has a longitudinal extent that is slightly longer than thedefined width of the gap.
 7. A device, comprising: a structure defininga gap having a gap width; a defined segment of nanotube fabric, disposedon the structure and spanning the gap, the nanotube fabric segmentincluding a plurality of nanotubes, at least some of said nanotubeshaving a length in excess of the gap width; and a clamp, disposed ateach of two ends of the nanotube fabric segment and disposed over atleast a portion of the nanotube fabric segment substantially at theedges defining the gap.
 8. The device of claim 7, wherein the clamp ismade of electrically-conductive material.
 9. The device of claim 7,wherein the clamp is made of electrically-insulative material having avia therethrough filled with electrically conductive material to providean electrical communication path with the nanotube fabric segment. 10.The device of claim 9 wherein the via is filled with metal to provide ametallic signal path to the nanotube fabric segment.
 11. The device ofclaim 9 wherein the nanotube fabric segment is made of a nanofabrichaving a porosity and wherein the electrically conductive materialfilling the via also fills at least some of the pores of the of thenanotube fabric segment.
 12. The device of claim 7, wherein the nanotubefabric segment has a lithographically-defined shape.
 13. The device ofclaim 7, further comprising an electrically-conductive trace disposed inthe gap and being in spaced relation with the nanotube fabric segment.14. The device of claim 7 wherein the clamp is a structure defining asecond gap above the nanotube fabric segment and wherein the gap and thesecond gap each have respectively a conductive trace disposed therein.15. The device of claim 7 wherein the nanotube fabric segment is made ofa nanofabric having a porosity and wherein the clamp is made of materialthat fills at least some of the pores of the of the nanotube fabricsegment.
 16. The device of claim 7 further including at least oneelectrically conductive trace in spaced relation relative to thenanotube fabric segment and wherein the nanotube fabric segment iselectromechanically deflectable into contact with trace in response toelectrical stimulation of the trace and nanotube fabric segment.
 17. Thedevice of claim 16 wherein the contact with the trace is a non-volatilestate.
 18. The device of claim 16 wherein the contact with the trace isa volatile state.
 19. The device of claim 16 wherein the at least oneelectrically conductive trace has an interface material to alter theattractive force between the nanotube fabric segment and theelectrically conductive trace.
 20. A method for making a device,comprising: providing a structure having a gap of defined width; forminga region of sacrificial material in the gap; forming a nanotube fabricsegment over the structure and region of sacrificial material; at eachend of the nanotube fabric segment providing a clamp over at least partof the nanotube fabric segment substantially at the edges defining thegap; and removing the region of sacrificial material so that thenanotube fabric segment is suspended over and spanning the gap, clampedat each end of the article.
 21. The method of claim 20 wherein thedefined length of the nanotube fabric segment slightly exceeds the widthof the gap.
 22. The method of claim 20 wherein the clamp is formed ofinsulative material.
 23. The method of claim 20 wherein the clamp isformed of electrically conductive material.
 24. The method of claim 20wherein forming the nanotube fabric segment includes forming a mattedfabric of nanotubes and removing a portion of the fabric to yield thenanotube fabric segment.
 25. The method of claim 24 wherein removing aportion of the fabric includes lithographically patterning and etchingthe fabric.
 26. The method of claim 20 wherein the nanotube fabricsegment is made of a porous nanofabric and wherein providing the clampincludes providing material that fills at least some of the pores of thenanotube fabric segment.
 27. The method of claim 20, wherein the clampis made of electrically-insulative material and the clamp is providedwith a defined via therethrough, and wherein the method further includesfilling the via with electrically conductive material to provide anelectrical communication path with the nanotube fabric segment.
 28. Themethod of claim 27 wherein the via is filled with metal to provide ametallic signal path to the nanotube fabric segment.
 29. The method ofclaim 27 wherein the nanotube fabric segment is made of a nanofabrichaving a porosity and wherein the electrically conductive materialfilling the via also fills at least some of the pores of the of thenanotube fabric segment.
 30. The method of claim 20, further comprisingproviding an electrically-conductive trace in the gap so as to bedisposed under the region of sacrificial material.
 31. The method ofclaim 20 wherein providing the clamp includes forming a structuredefining a second gap above the nanotube fabric segment and wherein themethod includes providing an electrically-conductive trace in the gapand the second gap.